1. Field of the Invention
The present invention is directed to an air blanket warming system for incorporating a remote temperature sensor mounted adjacent the air blanket to provide a temperature signal representative of the heated air delivered to the air blanket and includes an improved conduit unit, remote temperature sensor unit, and improved air blanket.
2. Description of Related Art
It is well known to provide heated air to portions of the human body to maintain the human body temperature and/or to provide curative heat treatment to a patient. Air blankets are frequently used in operating rooms and critical care units and include a disposable air blanket that can be formed from a thin plastic or thin plastic paper configuration with appropriate apertures on one side of the blanket to bathe a patient with warm air. During the operation, the temperature of the patient can therefore be controlled. In a post-operative setting, it is possible to treat the patient for hypothermia. The concepts and use of the application of both heated and cold air is well known such as shown in U.S. Pat. No. 2,110,022 and U.S. Pat. No. 2,601,189.
Air blankets or thermal blankets generally use a heater unit that is portable and includes a cabinet having operator controls for setting temperatures with an internal heater unit and blower unit for delivering a controlled temperature of air to a flexible conduit. The flexible conduit extends from the cabinet to the thermal blanket. A temperature sensor is mounted at the egress of the cabinet housing to measure the heated air for purposes of controlling the heater unit within the housing. The flexible conduit is replaceable and connects to an appropriate coupler port on an inflatable thermal blanket. The blanket is disposable and is usually offset from the heater or source cabinet by a distance of approximately 24 to 36 inches of flexible hose length. The temperature sensor that is within the cabinet is physically and thermally isolated from the inflatable blanket by the hose and also frequently by interspaced components such as filters and connectors.
The flexible hose diameter is typically 2xc2xd inches and the air flow velocity is from a range of 1200 to 2000 feet a minute. The temperature of the warm air delivered to the flexible hose ranges from approximately ambient temperature to 48 degrees Centigrade. If the room temperature is about 20 degrees Centigrade, there is a drop of about 4 degrees Centigrade that can occur at the highest delivered air temperature as the air flows in the hose to the thermal blanket. This temperature drop, however, is highly dependent on not only the room temperature but also any turbulence generated in the hose air flow due to bends in the hose. Additional descriptions of thermal blankets can be found for example in U.S. Pat. Nos. 5,324,320, and 4,660,388.
The prior art is still seeking to improve the warming air apparatus for addressing the issue of hypotherapy in patients undergoing surgery and to further assist in the re-warming process after surgery or prolonged exposure to cold environment.
The present invention provides a fluid blanket warming system or thermal blanket system that can be applied to a patient to address hypothermia and includes a blanket unit made of a light weight material such as plastic and/or plastic and paper having an approximately hollow core to form a plenum chamber for the receiving of a gas such as heated air. A coupling port is provided to enable the admission of the gas from a heat source. Generally, the heat source is in a portable housing cabinet that supports a heater unit for heating the gas and a blower unit for providing forced air to the heater unit. A control circuit controls the temperature of the heater unit and the air can be filtered as it enters into the cabinet and also as it leaves the cabinet. A flexible conduit can be removably connected to a port on the cabinet housing for the delivery of the heated gas to an inflatable blanket unit. The inflatable blanket unit can come in various configurations and shapes and can include segmented or channel sections to assist in erecting the blanket when it is heated. The inner surface of the thermal blanket adjacent to the patient will be porous to thereby pass the thermally controlled air to the appropriate application of the patient""s body. Regardless of the particular configuration or construction of the thermal blanket, it will have a coupling port for removable connection with the flexible conduit.
A temperature sensor unit is mounted adjacent the thermal blanket unit and is in direct contact with the heated gas received from the heater unit to provide a temperature signal that is representative of the heated gas, such as air, as it is delivered to the thermal blanket unit. The control circuit thereby can drive a heater unit and blower unit within the cabinet to provide a pre-determined temperature for the patient which will take into account any temperature loss from the heater unit across the flexible conduit to the thermal blanket.
In one embodiment of the invention, the temperature sensor unit can be mounted within a coupler that can connect to the coupling port of the thermal blanket. The temperature sensor unit can include a heat conductive support member extending across the flow path of the heated gas so that the temperature sensor can accurately respond to the actual temperature. This heat conductor member can be in the form of a cross arm configuration that is structurally formed from a plastic resin substrate cladded with a heat conductive metal, such as copper, stainless steel, nickel, etc. The temperature sensor unit can be mounted at the inter-connection or junction of the arm members and since the heat conductive arms extend across the flow path, it can accurately average the temperature regardless of laminar or turbulent flow at the entrance to the thermal blanket.
An alternative embodiment of the invention can have the temperature sensor unit mounted directly on a coupler that can be removably attached to a thermal blanket rather than having it attached to a coupler on a flexible conduit.
A further alternative embodiment can have the temperature sensor unit directly mounted on the thermal blanket.
In an embodiment of the invention, a conduit unit for fluidly interconnecting a thermal blanket with a housing having a heater unit can comprise an elongated flexible conduit with a first coupler at one end of the conduit configured for removable connection to the heater housing and a second coupler at the opposite end of the conduit configured for removable connection to the air blanket or thermal blanket. A temperature sensor unit is mounted to sense the temperature of the air heated by the heater unit as it exits the second coupler. An electrical connector can extend from the temperature sensor unit through the first coupler and can have an end or terminal portion adapted to be electrically connected to transmit a temperature signal from the temperature sensor unit to a control circuit so that the heater unit can be controlled to a pre-determined temperature for a patient.
Finally, a second temperature sensor can also be mounted to provide a redundant measurement adjacent the first temperature sensor and a safety alarm circuit can shut off the air warming system, if the temperature level extends beyond predetermined limits.